I never even thought of gettin worse gas mileage w/ RFG. Hmm...

 

on my 2003 5.3L ext cab it has just over 72K miles, only mods are 07 efans and bigger rad and a dynomax ultraflow muffler and on average i only get 15 MPG, now this past weekend over new years, i filled it up and drove to dallas and back to huntsville, 426 miiles and then to my place in humble and around town alittle and when i filled it up again before the low fuel light came on i had 507 miles amd it took 24.1 gallons to fill it up, and that was 21 MPG, best i have ever got and i had the a/c off got most of the trip. Wish i could get that kind of MPG more often.

 

well while i have run mixed fuel before, it was out of state. since then ive changes the fuel filter twice. also none of the gas pumps i use show the tag stating its mixed fuel.

 

no pumps in mn show that the fuel is mixed. there are only very few that say it is not mixed. it seems it has become the standard to mix and i believe Louisiana mixes since 1990 like most others.

 

Hey guys wanted to let you know that i will be filling up tomorrow and pulling a car to Grand Prarie, TX. Probably set the cruise at 75 and see what mileage it gets. Car is 97' camaro v6, no engine half an interior, but Ill have a 6.0 truck motor in the bed. Just dropping that off and running back empty trailer.

 

Mine has gone from 18.6 to 16 (combined) and from 20 to 17.5 hwy.

 

What made you drop from 18 to 16 and 20 to 17?

 

I don't know at this time.

 

In the winter in some locations, they add stuff to the gas that will lower mileage

 

tune and check your maf sensor it may be dirty.
did you oil your k&n?